Conventionally, various methods have been proposed which display 3-dimensional images. Of these, “binocular methods” using binocular parallax are generally used. Specifically, a stereoscopic vision is achieved by preparing left-eye and right-eye images having binocular parallax and projecting them separately on left and right eyes, respectively.
FIG. 23 is a conceptual view for illustrating a “time-division scheme” as one of the typical binocular methods.
In this time-division scheme, the left-eye image and right-eye image are arranged alternately, line by line, in vertically direction as shown in FIG. 23, so that the field for displaying the left-eye image and the field for displaying the right-eye image will be switched and displayed alternately. The left-eye image and right-eye image have half the vertical resolution compared to that in normal 2-dimensional display mode. An observer should put on shutter glasses that open and close in synchronism with the switching period of the display. The shutter used here opens the left-eye side and closes the right-eye side when the left-eye image is displayed and closes the left-eye side and opens the right-eye side when the right-eye image is displayed. With this arrangement, the left-eye image can be observed by the left eye alone while the right-eye image can be observed by the right eye alone, to achieve stereoscopic vision.
FIG. 24 is a conceptual view for illustrating another typical scheme of the binocular methods, namely “parallax barrier scheme”. FIG. 24(a) is a view showing the principle of the cause of parallax. FIG. 24(b) is a view showing an image frame displayed in the parallax scheme.
In FIG. 24(a), an image in which stripes of the left-eye image and stripes of the right-eye image are arranged in pairs as shown in FIG. 24(b), is displayed on an image display panel 2401 while a so-called parallax barrier 2402 with slits arranged at intervals of a corresponding distance for the image is placed in front, whereby the left-eye image is observed by left eye 2403 alone and the right-eye image is observed by right eye 2404 alone, to achieve stereoscopic vision.
In general, when a 3-dimensional image, not limited to “time division scheme” and “parallax barrier scheme”, is observed stereoscopically, easiness to create stereoscopic vision differs depending on the content of the image being displayed or the way of displaying. When, for example, with motion picture data, a video with rapid motions is viewed or special playback such as fast forward etc., is done, there occur cases where the user faces difficulties in understanding the content by stereoscopic vision because of the shortness of the time of one frame being displayed, though there are differences between individuals. There has been an example of a “stereoscopic motion picture compression encoding apparatus and stereoscopic motion picture decoding and reproducing apparatus” disclosed in the aftermentioned patent document 1, in which playback of a 3-dimensional image is displayed as a 2-dimensional image when in fast playback mode.
The operation of fast playback in the stereoscopic motion picture compression encoding apparatus and stereoscopic motion picture decoding and reproducing apparatus will be briefly described.
In the encoding apparatus, based on the left-eye image data and right-eye image data input through a camera or the like, reference image data is created first. Then, differences of the left-eye image data and the right-eye image data from the prepared reference image data are determined and output as left-eye differential data and right-eye differential data, respectively. These reference image data, left-eye differential data and right-eye differential data are compressed and encoded, and multiplexed to generate 3-dimensional image encoded data.
In the decoding and reproducing apparatus, the compressed 3-dimensional image encoded data is separated into reference image data, left-eye differential data and right-eye differential data. In normal playback mode, the reference image data, left-eye differential data and right-eye differential data are all decoded to generate a left-eye image from the reference image data and left-eye differential data and generate a right-eye image from the reference image data and right-eye differential data. With these left-eye image data and right-eye image data, a 3-dimensional image is reproduced. On the other hand, in fast playback mode, only the reference image data is decoded to reproduce the reference image as a 2-dimensional image.
Incidentally, this is also applied to the case of still image data; when the resolution of image data is higher than that of the display screen, it is only possible to display part of the image data if nothing is done. To deal with this, it is necessary to do scrolling to display the desired area of the image data. For example, if an image having a markedly great spatial resolution, such as map image data is displayed, the scrolling function is essential. Also, recent mobile phones, PDAs and the like have a miniature display for image display, and the scrolling function is essential for displaying images on such a mobile device.
Patent Document 1:
Japanese Patent Application Laid-open Hei 7-327242